Chapter 2 - Integrated weed management in organic farming

Abstract

Organic farming has a pedigree stretching back over a century and is now increasingly a role model for how mainstream agriculture needs to change. Integrated weed management (IWM) uses all the sciences, physics, chemistry, biology, and ecology in a holistic/systems-based approach to manage weeds. The old idea that particular plant species are weeds needs to be abandoned and replaced with an understanding that weeds are “value judgments,” and the judgment needs to be made on a case-by-case basis if a particular plant or population is causing significant harm. A good understanding of weed biology and ecology is essential for effective organic IWM and in particular the role of the weed seedbank. The hierarchy of weed management tools starts with managing weed seed rain and the seedbank, then moves through rotations, plants versus weeds, soil management, crop and pasture choices, pre-crop emergence weeding, particularly false and stale seedbeds, crop establishment techniques, and concludes with post-crop emergence weeding, which is considered the icing on the cake of integrated weed management. The range of post-emergent weeding machinery continues to grow, with completely new machine designs still being developed, compared to the stagnation of herbicide discovery. The diversity of weeding machines is classified first into contiguous and incontiguous, the former that weed the whole field surface, the latter have gaps for crop rows. Incontiguous is further subdivided into interrow and intrarow weeders. The pros and cons of “intelligent” computer-controlled intrarow discriminatory weeders versus simple mechanical intrarow nondiscriminatory weeders are discussed. In the last 2 years, advances in artificial intelligence have facilitated a revolution in robotic weeders. Equally, electrothermal weeding is also shaping up to be a revolutionary technology. The chapter concludes with weed management options for perennial crops.